Every pregnancy surgical emergency in a Belgian bariatric study followed an intestine-rerouting operation

A nationwide Belgian study has counted, for the first time across a whole country's maternity system, how often women who have had bariatric surgery face a surgical emergency while pregnant, and what happens when they do.

The work was published in BMJ Open on August 20, 2026. Researchers collected cases prospectively, meaning they recorded them as they occurred rather than searching backward through old files, from January 2021 through December 2022. Participating units covered 67.6% of Belgian maternity services and 65% of all births in that period.

Internal hernia accounted for 25 of the 35 complications

Thirty-three women experienced 35 surgical complications. The most common by a wide margin was internal herniation, with 25 cases.

An internal hernia is a specific hazard of operations that reroute the intestine, such as Roux-en-Y gastric bypass. Rerouting leaves gaps between loops of bowel inside the abdomen. A section of intestine can slip through one of those gaps and become trapped, which cuts off its blood supply. It is a surgical emergency. In pregnancy it is harder to spot, because the growing uterus shifts the organs and because abdominal pain and nausea are common in pregnancy for ordinary reasons.

The average point of diagnosis was 27 weeks and 6 days of pregnancy, in the third trimester. Every woman in the study went to surgical exploration within 24 hours. Two needed part of the bowel removed.

The authors state that all reported complications occurred after procedures involving intestinal rerouting, predominantly Roux-en-Y gastric bypass. Sleeve gastrectomy, which removes part of the stomach but does not reroute the intestine, did not produce cases in this cohort.

No mothers died, but 13 births were preterm and one newborn did not survive

Maternal outcomes were reassuring on the most serious measure. There were no maternal deaths, and one woman required intensive care.

Outcomes for the pregnancies were harder. Caesarean section occurred in 48.5% of cases. There were 13 preterm births, meaning delivery before 37 weeks, and one neonatal death.

The authors' conclusion links those two halves together. Prompt surgical management was associated with low maternal illness and no deaths, but frequently resulted in preterm birth and emergency caesarean section. They write that the findings highlight the need for a low threshold for surgical evaluation of abdominal pain in pregnant women with previous bariatric surgery.

Rare events, and this study cannot say how rare

The authors describe these complications as uncommon. That framing matters, because 33 cases across two thirds of a national maternity system over two years is a small number against the many pregnancies in women who have had bariatric surgery.

The study design also sets a hard limit on what can be concluded. Researchers counted women who presented with a complication. They did not count all pregnancies after bariatric surgery, and they did not compare procedure types against each other with a denominator for each. So the finding that every case followed a rerouting operation does not by itself establish a rate for bypass, and it cannot be turned into a numerical risk comparison between bypass and sleeve.

Coverage was incomplete, at 67.6% of maternity units, so cases in non-participating units are missing. The data covers two years in one country, and referral patterns and surgical practice differ elsewhere.

The authors call for balanced counselling about the benefits and risks of different bariatric procedures in women of reproductive age. That is a conversation for a patient and their own surgical and obstetric team, and the numbers here are one input to it rather than an answer.